Background: Disease-specific ankylosing spondylitis (AS) indices, including BASDAI (Bath AS Disease Activity Index), BASFI (Bath AS Functional Index), ASDAS (AS Disease Activity Score), and BASMI (Bath AS Metrology Index), are widely used in clinical trials and in some clinical settings, but not in most routine care. Laboratory tests usually are the only quantitative measures included in routine care of AS patients, but often are poorly informative. Routine Assessment of Patient Index Data 3 (RAPID3) on a Multidimensional Health Assessment Questionnaire (MDHAQ) is feasible and informative in many rheumatic diseases.
Objective: The aim of this study was to compare RAPID3 to BASDAI, BASFI, ASDAS, and BASMI in a cross-sectional analysis of 85 Korean AS patients collected in routine care.
Methods: MDHAQ/RAPID3, BASDAI, and BASFI were completed by patients, and ASDAS and BASMI assessed by health professionals. Indices and individual measures were compared using correlations, cross tabulations, scatter plots, and κ statistics.
Results: RAPID3 scores were correlated significantly with BASDAI (ρ = 0.82) and ASDAS-ESR (erythrocyte sedimentation rate) (ρ = 0.76), at levels similar to the correlation of BASDAI with ASDAS-ESR (ρ = 0.81). All 21 patients with BASDAI scores of 4 or greater, indicating active AS, were among 39 patients who had RAPID3 scores of greater than 12, indicating high severity, whereas 79% of 33 patients with ASDAS of greater than 1.3, indicating high activity, had RAPID3 high severity.
Conclusions: RAPID3 gives similar information to BASDAI and ASDAS in AS patients, in this limited cross-sectional study from 1 setting. Ankylosing spondylitis-specific measures are needed for clinical trials, but poorly feasible in most busy clinical settings. The MDHAQ/RAPID3 offers pragmatic quantitative clinical assessment of AS patients in routine care.